The External Objects documentation describes a cross-org adapter that:
Uses the Lightning Platform REST API to access data that’s stored in other Salesforce orgs.
Can this (or some other technique) be used to adapt local custom objects?
(Wondering here about External Object definitions that are related to each other pulling in local custom object data rather than external data. Then logic built around the External Object field name of say
ExtObj__x.Abc__x could actually be working against the local custom object field of say
CusObj__c.Xyz__c. The External Object is as acting as an adapter.)